New quake, Tsunami warning for Japan

TOKYO — Japan was rattled by a strong aftershock and tsunami warning Thursday night nearly a month after a devastating earthquake and tsunami flattened the northeastern coast.

The Japan meteorological agency issued a tsunami warning for a wave of up to 6 feet. The warning was issued for a coastal area already torn apart by last month’s tsunami, which is believed to have killed some 25,000 people and has sparked an ongoing crisis at a nuclear power plant.

Officials say Thursday’s aftershock was a 7.4-magnitude and hit 25 km under the water and off the coast of Miyagi prefecture. The quake that preceded last month’s tsunami was a 9.0-magnitude.

TSUNAMI BULLETIN NUMBER 001
PACIFIC TSUNAMI WARNING CENTER/NOAA/NWS
ISSUED AT 1439Z 07 APR 2011
THIS BULLETIN APPLIES TO AREAS WITHIN AND BORDERING THE PACIFIC
OCEAN AND ADJACENT SEAS...EXCEPT ALASKA...BRITISH COLUMBIA...
WASHINGTON...OREGON AND CALIFORNIA.
... TSUNAMI INFORMATION BULLETIN ...
THIS BULLETIN IS FOR INFORMATION ONLY.
THIS BULLETIN IS ISSUED AS ADVICE TO GOVERNMENT AGENCIES. ONLY
NATIONAL AND LOCAL GOVERNMENT AGENCIES HAVE THE AUTHORITY TO MAKE
DECISIONS REGARDING THE OFFICIAL STATE OF ALERT IN THEIR AREA AND
ANY ACTIONS TO BE TAKEN IN RESPONSE.
AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS
REPORTED BY THE JAPAN METEOROLOGICAL AGENCY.
ORIGIN TIME - 1432Z 07 APR 2011
COORDINATES - 38.2 NORTH 142.0 EAST
DEPTH - 40 KM
LOCATION - NEAR EAST COAST OF HONSHU JAPAN
MAGNITUDE - 7.4
EVALUATION
NO DESTRUCTIVE WIDESPREAD TSUNAMI THREAT EXISTS BASED ON
HISTORICAL EARTHQUAKE AND TSUNAMI DATA.
HOWEVER - EARTHQUAKES OF THIS SIZE SOMETIMES GENERATE LOCAL
TSUNAMIS THAT CAN BE DESTRUCTIVE ALONG COASTS LOCATED WITHIN
A HUNDRED KILOMETERS OF THE EARTHQUAKE EPICENTER. AUTHORITIES
IN THE REGION OF THE EPICENTER SHOULD BE AWARE OF THIS
POSSIBILITY AND TAKE APPROPRIATE ACTION.
THIS WILL BE THE ONLY BULLETIN ISSUED FOR THIS EVENT UNLESS
ADDITIONAL INFORMATION BECOMES AVAILABLE.
THE JAPAN METEOROLOGICAL AGENCY MAY ALSO ISSUE TSUNAMI MESSAGES
FOR THIS EVENT TO COUNTRIES IN THE NORTHWEST PACIFIC AND SOUTH
CHINA SEA REGION. IN CASE OF CONFLICTING INFORMATION... THE
MORE CONSERVATIVE INFORMATION SHOULD BE USED FOR SAFETY.
THE WEST COAST/ALASKA TSUNAMI WARNING CENTER WILL ISSUE PRODUCTS
FOR ALASKA...BRITISH COLUMBIA...WASHINGTON...OREGON...CALIFORNIA.
=================================================================

For those of you with Google Earth, the epicenter has been marked up by Google. It’s a lot closer to shore than the original, and can only be called an aftershock at magnitude 7.1 by comparison to the much larger 8.9 magnitude monster EQ.
A 2 meter tsunami shouldn’t overtop the tsunami walls.

I thought my house was going to shake apart. (I’m in east Koriyama city, Fukushima, and house is 54km due west from the Fukushima Dai-ichi nuclear power plant).
0113hrs as I type this and waiting for my nerves to calm down.
Regards
Kevin.

Current situation at 0116hrs JST : No tsumani observed as of yet however a minor change in sea level detected in one area, and no tsunami disaster expected. Tsunami warnings lifted.
No further damage or further anomalies in the Fukushima nuclear reactors.
Onagawa nuclear power plant in Miyagi has lost 2 out of 3 external power transmission lines supplying it, after it was shut down safely after the 11th March quake.
More intense aftershocks are to be expected.
Power outages across all of Aomori, Iwate, Akita; also parts of Miyagi, Yamagata
My own lights flickered lots about 10 seconds before the seismic waves hit my house.
Power still operating in Koriyama city.
My nerves are still quaking.
Regards
Kevin.

Thank you very much for your updates, Kevin.
Cool observations under pressure – or under shakings, external and internal – are extremely valuable, and tell more than a press notice.
I hope you, your friends and family are ok.

Jay Davis says:Someone, somewhere has mistranslated something. Nowhere on earth is there water 25 miles deep.
Not sure but I think it means depth in the crust, not depth in the ocean. Although that’s still pretty deep.

“Depth” in this case means the actual location — the focus, or hypocenter — of the quake. They’re saying the actual break in the rock occurred 25 miles down. The “epicenter” is the point on the Earth’s surface directly above the focus.

“Depth” is how far down in the earth the tectonic rupture occurred, i.e. Where the actual slipping of rock against rock happened. Latitude, longitude, and depth define the 3d location of the quake which is called the “hypocenter”. The “epicenter” is the projection of that 3d point vertically to the surface — the point directly above the hypocenter.

Some of you may remember one or two of my posts in the previous earthquake thread, when I started a daily updates of quakes and geomagnetic activity, prompted by the New Zealand’s earthquake.
Data isn’t yet sufficiently numerous to have any pronouncements.http://www.vukcevic.talktalk.net/EQr.htm
Updates are at 8am UTC (results plotted refer to the previous 24h)

Depth of 25 km.
Clearly, it cannot be the depth of water. I strongly suspect this is referring to the depth in the solid earth i.e. the depth starting at the sea bed and going down.
Earthquakes are common at subduction zones well below the ocean bottom. The subsiding plate “sticks” for a while, stress builds up and something gives to produce the earthquake.

Since it’s quiet and all those people who know better than me aren’t putting it out there, the use of ‘depth’ seems quite correct.http://en.wikipedia.org/wiki/Earthquake
“The majority of tectonic earthquakes originate at the ring of fire in depths not exceeding tens of kilometers. Earthquakes occurring at a depth of less than 70 km are classified as ‘shallow-focus’ earthquakes, while those with a focal-depth between 70 and 300 km are commonly termed ‘mid-focus’ or ‘intermediate-depth’ earthquakes.”
Bolds are my own. I admit it’s only my guess that all earthquake depths are measured from sea-level whether quakes occur under the ocean or beneath exposed land but it would be interesting to know for sure if anyone could confirm or correct me on that.
Further to the above question, would I be right in guessing that these depths are determind by following back the various measurements of the shockwaves to their starting point using Time Delays?

Kevin Cave, thanks so much for the updates!
Are you close enough to the coast (54 km) to be directly affected by the shelters? I would think anyone with relatives or friends would move there first if possible. I’ve been following this every few hours since the big one hit.

Anyone know the depth level where rock is too ‘bendy’ to crack and cause an earthquake ? Rock sitting all those miles down ought to be very hot and under enough pressure to become be soft and pliable , so why does it crack and not just stretch ?

According to the Wikipedia page titled “1700 Cascadia Earthquake,” there have been six major earthquakes off the Pacific Coast since 600 BC that are capable of causing the extreme devastation equivalent to that seen in Japan all the way from Northern California to Northern British Columbia.
Those dates are: 600 BC, 170 BC, 400 AD, 810 AD, 1310 AD, and 1700 AD. From this sequence it is possible to say that the average interval between events is 460 years (five intervals) and it appears possible to construct a linear sequence of 460 year-separated dates beginning at 575 BC with no more than a 55-year error from any real event. It looks like we might expect the next one within 75 years of 2185 AD — No guarantee however!

duncan b: It appears to be dependent on where the report comes from, herewith the description from the USGS site:Depth
The depth where the earthquake begins to rupture. This depth may be relative to mean sea-level or the average elevation of the seismic stations which provided arrival-time data for the earthquake location. The choice of reference depth is dependent on the method used to locate the earthquake. Sometimes when depth is poorly constrained by available seismic data, the location program will set the depth at a fixed value. For example, 33 km is often used as a default depth for earthquakes determined to be shallow, but whose depth is not satisfactorily determined by the data, whereas default depths of 5 or 10 km are often used in mid-continental areas and on mid-ocean ridges since earthquakes in these areas are usually shallower than 33 km.
I’d always considered it as measured from Average Sea Level.
Kevin – stay safe, and thank you for the updates.

In answer to a holmes, 12:08 pm
Earthquakes at subduction zones occur in a band parallel to the line along which the plate dips into the underlying rock layers. This is called the Wadatti-Benioff zone. Earthquakes are common (and shallow) where the plate is near the surface but stretch back into the hinterland at increasing depths. The depth where earthquakes finally disappear varies in different locations but is typically when the subducting plate reaches a depth of 100-200 km. At some subduction zones there are “outlier quakes” as deep as 600-700 km.
There is no single type of subduction zone.

Who will worry now about “climate change” or GW, or, worst about Al´s prophesies? He did not forecasted this earthquakes´ series (he was too busy with counterclockwise Big Storms business.-always invariably progressing to the left-..).

The quake came at 23:32 local time, Thursday 8 April. Even Tokyo was shaken strongly.
Near the epicenter, about 100 people were injured (probably nobody was killed), and 4 million homes underwent electricity shutdown. The evacuees, still 150 thousand and many are without municipal water supply and sufficient heating, may have been frightened tremendously in darkness.

Hi, just a quick update now that I got some sleep 😉
0856hrs JST
Apart from the lack of power in some areas in northern Japan, there seems to be no major problems in the country.
It looks like in total there were about 100 people injured throughout the region. No deaths reported from what I could make out watching the news this morning.
Viv, yes me and my family are all okay, thanks for your concern.
If I hear of anything dramatic I’ll let it be known here.
Regards,
Kevin.

I was scheduled to give a lecture (on AGW!) to 30 to 50 high-school science teachers on 26 September in Fukushima City, but the contact person emailed me a couple days ago that their facility had been damaged (mechanically, not radioactively) so that my lecture had to be cancelled.
To Kevin: my son, a medical doctor, worked at a hospital in Koriyama City until three years ago. He is now in Utsunomiya, Tochigi Prefecture, which is nearer to the epicenter than Tokyo is.

1125hrs JST
NHK now reporting that 2 people died because of Thursday night’s strong aftershock; a 63 years old woman in Yamagata, and a 79 years old man in Miyagi. I have no details on why those deaths ocurred.

Checking in. I live in Yamagata.
Here, this earthquake was was similar in magnitude (5-) to the earlier one but different in form. The first earthquake had a long period of P waves, a distinct pause, then a second period of S waves. This one was much shorter in duration, with no break between arrivals. In addition we had noticeable vertical (ground roll) motion. It was clearly a smaller event, but much closer. Lying in bed and being thrown up in the air certainly got my attention.
We had no damage at home, but I have a pile of CDs to clear up. No damage at the memsahibs factory, but all the machines and workbenches have shifted around. Power was off until about 9 this morning. Water won’t be back on until tomorrow, as the treatment process needs to be re-started.
Our emergency kit (torches, candles, radio) was at hand, no problems there. My first job was to fill the bath with water, while it was still running. Job done, we have enough for several days. For anyone living in an earthquake-prone area, if you are intact after the event, make filling the bath your No1 priority.
The trains have stopped running while the line is inspected for damage. Schools are closed (yay). There is no sense of crisis in town. There are short queues for fuel, but nothing like last time. Our factory is running and our shops are open for business. Life goes on.

In the light of hindsight; it seems that construction of a nuclear power plant on a tsunami prone ocean shoreline seems to be an incredibly bad idea. Even the east coast of the United States is said to be at risk of a potential 30 to 100 ft. high kinetic impact tsunami that might be generated during a future eruption near Cumbre Vieja on the volcanic ocean island of La Palma, in the Canary Islands if a large unstable portion of the old volcano were to avalanche into the sea.
It is rather ironic that one consideration in development of Japan’s nuclear power policy has been the reduction of CO2 emissions. We can only hope that they will be able to clean up this mess and dump the contamination in sealed containers somewhere like the bottom of Japan Trench where it might eventually be subducted into the asthensophere. I think it is in the vital interest of everyone in the world to contribute to the resolution of this problem.
Canary Island Mega-Tsunami (History Channel)

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